On 7/17/20 7:46 PM, Qu Wenruo wrote:
On 2020/7/18 上午4:42, Josef Bacik wrote:
Autodefrag is very useful for somethings, like the 9000 sqllite files
that Firefox uses, but is way less useful for virt images.
Unfortunately this is only available currently as a whole mount option.
Fix this by adding an "autodefrag" property, that users can set on a per
file or per directory basis. Thus allowing them to control where
exactly the extra write activity is going to occur.
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
- This is an RFC because I want to make sure we're ok with this before I go and
add btrfs-progs support for this. I'm not married to the name or the value,
but I think the core goal is valuable.
The idea looks pretty good to me.
Although it would be much more convincing to bring some real-world micro
bench to show the benefit.
The same benefit as what existed originally for autodefrag, firefox isn't
unusably slow on spinning rust.
However I still have a concern related to defrag.
Since it's on-disk flag, thus can be inherited by snapshot, then what
would happen if an auto-defrag inode get snapshotted.
Would any write to the auto-defrag inode in new snapshot break the space
saving?
Sure but that's the case for all defrag, and this is in fact better than mount
-o autodefrag because you can limit the damage. Thanks,
Josef
